As Lynne Cox shows in her new book South with the Sun: Roald Amundsen, His Polar Explorations, and the Quest for Discovery, each chapter in Amundsen’s life was a big step closer to the South Pole – and contributed to his understanding the extreme challenges and dangers of polar exploration.

But Cox wants her book to be more than just a biography of an explorer. She states in her Preface: “[P]eople, places, things from the past [are] guides, as true and dependable as the stars, the planets, and the sun that guide great navigators across the earth, seas, and heavens.”

Cox interweaves segments about Amundsen and the explorers who prepared the way for him with extensive narration about cold-water distance swims she has made in places Amundsen would have known. The intent, as she describes it, appears to be to show how Amundsen, and the others, have been “my waypoints and my inspiration.”

Nonetheless, a reader keen to learn about Amundsen may become frustrated. For the most part, the endless, diary-like details about her swims are a poor fit with Amundsen’s great journeys – diversions that neither forward an understanding of Amundsen’s life nor provide convincing evidence that Amundsen serves as a waypoint for hers.

That’s too bad! Before “South,” she wrote two excellent books specifically about her swims. First was “Swimming to Antarctica,” which detailed many of her long-distance and cold-water swims in gripping detail, leading up to her astonishing 25-minute, 1-mile swim in Antarctica. “Antarctica” is a page-turner, with brilliant descriptions of her swim environments and locations. Then there is the wondrous “Grayson,” about swimming with a baby gray whale off the California coast.

Separating out much of the material about swimming in “South,” along with the chapters at the end about today’s challenges flying to the South Pole, there is a core book here that is vivid and compelling.

Cox describes in horrifying detail how Amundsen, as a young man, almost perished in the snow. One winter he and a friend went skiing along a plateau west of Oslo, Norway. They took insufficient food and equipment, became lost, and when night fell Amundsen built himself a snow cave. Melting snow formed ice, which entrapped him, and if not for the efforts of his friend, Robert Falcon Scott would now be credited as being first to the South Pole.

(Scott reached the South Pole only five weeks after Amundsen conquered it. He and his team, having discovered Amundsen had gotten there first, perished of cold and hunger on their way back to base camp.)

Much of “South” is given over to telling the story of Amundsen’s crossing of the Northwest Passage – a first as significant as reaching the South Pole. Cox juxtaposes this with extensive details of frigid swims she makes along his route – accounts of sporadic interest, engaging mostly only in that they provide a view of these isolated, icy places today.

When the team passes the point Ernst Shackleton reached before turning back – further south than anyone else had been before – “Amundsen was overcome with emotion, more than at any time during the journey. Tears filled his eyes....” Finally, Amundsen and his team crossed a 9-thousand foot plateau and reached the South Pole.

Cox is an extraordinarily talented swimmer/writer. Here’s hoping her next effort is a return to form.